On Thu, 2021-04-01 at 12:48 +1000, Erwin van Londen wrote: > > > > Benjamin has added a marginal_path group(multipath marginal > > pathgroups) in > > the dm-multipath. > > https://patchwork.kernel.org/project/dm-devel/cover/1564763622-31752-1-git > > -send-email-bmarzins@xxxxxxxxxx/ > > > > One of the intention of the Benjamin's patch (support for maginal > > path) is > > to support for the FPIN events we receive from fabric. > > On receiving the fpin-li our intention was to place all the paths > > that > > are affected into the marginal path group. > I think this should all be done in kernel space as we're talking sub- > millisecond timings here when it comes to fpins and the reaction time > expected. I may be wrong but I'll leave that up to you. Sub-ms latency is impossible with this setup (kernel -> broadcom FC daemon -> multipathd -> kernel). It's only suitable for "fatal" FPINs that would suggest taking a path offline on the time scale of minutes. I suppose that would work well for LN FPINs, but not for the other types. > > > > On receiving the congestion notifications our intention is to > > slowdown the > > work load gradually from the host until it stops receiving the > > congestion > > notifications. > > We need to validate the same how we can achieve the same of > > decreasing the > > workloads with the help of dm-multipath. > Would it be possible to piggyback on the service time path selector > in this when it pertains latency? Not on service-time itself, but someone could write a new path selector algorithm. IMO we'd still have the problem that this would be seen as a layering violation. In the long run dm-mpath may need to add transport- specific callbacks. But for a proof-of-concept, a selector algorithm with layering violations would be ok, I believe. Regards Martin -- Dr. Martin Wilck <mwilck@xxxxxxxx>, Tel. +49 (0)911 74053 2107 SUSE Software Solutions Germany GmbH HRB 36809, AG Nürnberg GF: Felix Imendörffer -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
